Glide path antenna



Sept. 9, 1952 Filed Feb. 28, 1948 c. B. WAT-rs, JR 2,610,321

GLIDE PATH ANTENNA s sheets-sheet 1 JNVENTOR. c//fsrE/P Mirza ATTORNEY Patented Sept. 9; 1952 l CliesterB. Watts; J-rlf, Indianapolis, assignor to International'` Standard Electric Corporation, Y New York, Nijl.,` a corporation of Delaware liiapiic'ationrtiuary 28,1948, segialNofiaool This' inventionrelates to navigation'systems andmore particularly to" anjarrangement forlthef` guidance of Va craft alonga glidepath4 zone or :una` .1,

' `Previous instrument landing systemsV have utilizedthe equisgnal f method or' directl ampli-l tudefcomparison method'forwproviding either a straightiline glide path obtainedfr from atransmittel installed'at the far end of theruntvay or:

afglide pathV or zone 'having' a hyperbolic `characteristic 'frornv a transmitter ldis'pla'cedr tofone"` sidelof'the runwayl@` 1 For the present condition of? aviation-16mgv run= ways areneeded andi the latter type of glide path beaconsis favored as itidoesnot presenta'noberstruction to landing.` fgzHowever. 1 because :of 'fthe displacement the glidepatl does'notreach? down'f' to .the .ground at the region of .touchdownlunless special `shaping of the-patternsV is provided.` Heretofore, this has been accomplished byV alter-- ing the radiation patterns-oftheprincipal glide path radiators.` .This requires:A trial and terror methods: vof adjustment, since the .principal 4,radiation patterns are quite powerfuland local con ditions may. strongly aiectitheegpattern1in; the

vicinity of the runway.

It is therefore an objectof this.-iru/ention-to` provide an improved arrangement.forproducing.` and modifying predetermined .radiation `patterns for thev guidance of4 a craft along .a1 prescribed course from units spaced laterallyirom thezrun Way;

. Inaccordance with an embodiment of myfinvention, a glide patharrangement,provided ask a single unit,is installed -on one side of therun-.z

way in thelvicinity. of the point fof Acontact of aircraft uponlanding for transmitting radiant energy defining the normal; glide path course having a hyperbolic characteristic. In the viv cinity of the point of contact the hyperbolic characteristic is modiiied to provide themore desirable straight lineV path by a radiant energy transmission from a modierunit in the glide path arrangement. y

YThe above3mentioned and other vfeatures and objectsrof this invention will become .rnoleeapeY parent and the invention itself, thoughnotnecessarly defined by the said featuresv andY objects,

will be ,best understood by reference to the lfollowing description o f an embodiment of the 4inventiorrl taken in "connection with thejaccom-` panying drawings whereling:

Fig. 1 illustrates in schematic form glitjlepath'. accordancewith the present iny arrangement in vqntipr L Fig. 2

hows "in schematic yforrnthe antenna system providing the required radiation `patte rn range or"J for A.producing a the lglide` 'path' course indication. Fig. 3 shotfs'aseries of waveforms used in 'exi plaining the "functioning of the antenna systenil OFgZ- .l vv iFig. 4 illustrates a waveformf explaining the operation'foffth "modifierarrangementof the antenna' systeinfot A Fig'.` 2.1 Figf arrangement for" producing radiant energy pat? terns in vacc'o'rr':la`.`ric'e'with' the invention.

, Accordi' 'gto Fig. 1 ltheglide pathantenna sys-` glelun'it preferably `hurl-- resultsin markedly reducingtiie obstaciestojaifg craft. The arrays' 'usedfhave' Soi little massk that it may possible tostrilre' them with the l'and ing edges "of 'anaircraft "flightwithout resulting in mre'thanminor damage to theaircrait;A

Tests also indicate 'that' at 'these frequencies' increased performance can be expected with'regardto theireedom from precipitation y effects suchasrairi or snow, as' well-Vasthe contour of the ground. The design ofthe Vantennajvleys'tern ofthe presentinvention places the lower antenna at half'thefheight oi theupper antenna.y nl-i'nthis arrangement, the efectiveheight of the upperA antenna'above ground" determines the path angle rather than a combination of the effective heights of the-upper and lowerantennas. "A very appreciablels'now all will, therefore, not s'eriouslyin-y terfe're with the operationof -this equipment-umless Vthe-'eiiectiveheight ofthe lower antenna is reduced -tov afraction 'of its normal height above' ground. 1 V

-The principles incorporated in this glide path arrangement makes'it possible to calculate the array design inrorder to produce a straight line or any other desired path to the point of contact. Informer systemsfa straight line path had to be 1 obtained entirelyby trial anderror methods. VA

`further advantage of this system, since the array toproduce the straight linepath is calculable, is

thatthe. equipmentcan be placed considerably further rom thecenterline of the runway. and

stillfobtainthefsame desirable path characteris- AE.tics over thecomplete path length. The design `ofthe antenna; Systemvyis such that considerablelatitude isfpermitted inthe selection of sites'onl either; side of y the point of contact.

-'l`he. antenna `system-.0i the presentA 'hoveri-` tion'diiiers considerably from that of previous shows lm block diagram' form a neun systems. The antennas inherently produce a straight line path and use the null and reference pattern method in forming the path, rather than direct amplitude comparison. As shown in Fig.

2 the glide path antenna system comprises an 5 upper array .`3, .preferably horizontally polarized,

. located ata height of a pluralityJef Lwavlfelengths at the carrier Afrequency above ground. In a preferred model the height selected was 12 feet.;P A fer a 2% degree path in a glide path system operi0 l ating substantially at 1000 megacyclespeI-Lsec-l -l ond. In this case the vertical, radiation pattern in the'antenna. array 3 whichwilllbelpduced.

by ground reflection is shown aseurvell loffflv-1'g.:3f It should be notedv that this pattern has a null 15 at the path angle of 21A degrees. 'The-antenna system of Fig. 2 further comprises a lowerantenna, array 4 which is located directly/below '3" at substantially half itsY height. The vertical pattern of array 4produoedby groundpreifl'ection 20 i's'j approximately'shown a'sfcurve 'Bf in'Fg. 3.1,' It should' be'noted thatY this ipatternhas a 'maxi-A mum at the pathangle. The addition and-"sub1 traction of the energyof'arrays 3 with the" energy ofarray 4 produces the total ,radiationjpatterns 25 ClL and C2 shown in Fig.j3. i. The intersecti'on'jof CI and C2A isthepglidepath. AFig. 3illustrates the situation only in the approach' directionwith ,Y

only an upper and lower* array asA described' and results in av 'hyperbolic fglide path characteristic. fIn` vorder to modifyfthe hyperbolic' character-- istie inthe vicinitydoffthe point of contact andVK providetheI 'more Vdesirable` straight` linen path v in. ythis region, a' modifler ga'ntennaarraylis pro#A "i" vided. This modieranteinalarray, also. ,serves thej -purpose of modifying the verticalv radiant energy, pattern'in thelazi'muth direction inorder' topr'o'vide the 'glidefpath to groundl since the glide path antenna systemis located to 'one side ofV the course. .Referring .to Fig.,.2.`j reference numerals 5 and 6 represent the modifier array, preferably c'omprisinglhorizontally .polarized units spaced'f1/ .wavelength from' eachl'` otlierV 'at .the carrier frequency p andvsojmontedas to` have their effective c'eter'of radiation directly. under array r3 at a ysmall distance h below. the lower' orthe .path` to, decrease. as the.. .functioneos 19.-@ A

being. the azimuth; angle from .ai linenerallel to,

therunway. This; isthe. required. condition; for so a. straight line path', :Fig-,.4 showsthepettem of vthe modifier plotted in.reetansular-coordinates- .It may be noted in. Eig.'4 3. that-a false pathf reverse sensing exists i, at .about.. 6.3/1. idglees.. Or'

threev timesthe: trueppathsangle. z Downsignals 65 predominate between thisfalse path; and the. true. path angle at 2% degrees; except: at 4.1/2 degrees, Where there is anaabsence.of"allssignals.. VIf .this

condition .provesy objectionable,aswatnping or 7o auxiliary antenna may be -addedl toi-the glidevv path antenna system. Methods .for-modifyinga..` pattern -to eliminateA false coursesfare described f inthe Patent 2,379,442l to yA'. G. K'andoian,l en- 4 swampiiig antenna may be provided as part f the single unit of the glide path antenna array to radiate additional high angle signals carrying downward modulation, which fill in the null at 41/2 degrees and extend the region of non-am# found -by' experience thatglide:` paths steeper than 5 degrees are very difflcult to follow, and are :not likely to be confused with the true path.

Injaddition. the reverse sensing of the first false path #716% degrees will result in both human Vand.a.utQ1I!tt0.Pilotiiying away from the falsey .Daih.

fReIerringtoZF-igure 5, the components of a Y.transmitter energizing the antenna system of Fig.'"2'comprise afcrystal oscillator 1 which is usedtdinsure the frequency stability of the final carrier frequency energy. A chain of harmonic multipliers ,8, VSand I0 controlledwby the crystal Oscillator. 1 .are essere feedy the carrier emplier.

VI l. and sub- A,carrier lbridge-for carrier sideband generator I2. In order to identify the coin-i ponentsrof the; glide` path patternLseparate modulation frequenciessuchgas f-LgandV ,f2 are pro-l. vided. 4.The yrelative velues: of, ffl and. f2.. should.. be maintained; constant, .may .be achieved by. providing forrexamnle two RCosei11atorsa-ffl3 I. and Manso Vchosen-thatl their-.difference yin .fre-f;

queney is equalto fhandthen .sumto f2.. iflhef. 0 RC oscillator outputs are mixed 1in; the mixer.

circuit tand ampliiied,...V .Themixingaction-,pro duces components ,offjli and; f2. whicnfare; sep-v a aratedpinpnlter circuit; t6; and `I'I. and adjusted to. be equalby; suitablepmeanssuchiasa lossnet.. work inc o'ne'g fiilteri 'l If.`.1the.1le.v el .of. either. LRC oscillator changes, .it i-willsproduce .equa1;varia1:

tions in the; inagnitlidefaof'y Jlv and JZfy withlmo te resultant` course'. shirt.` r; 1.;

..- The .imodulatingt frequency outputs. A.f l. 'and @f2 0 arefed into opposite terminals. of a:.'1 rw'fr.equency` bridge: .1.8.. This bridgermay. .consist of a1 hybrid..

coil A.or :its electrical= eguivalent: :Amplifiers vl 9 1-1' andn 2 0 -i are connected.. to v.thenutputrterminals' of the low frequency bridgetov .amplify '.thec'orn--l 4f binedmodulating irequencies. Amplifier 2l! receives f .equal magnitudes; of ffl. and `J2\ both; in, their originalphase.. s :These waves then modulate v theA carrier amplier l I :.Amplie'r .modulator I9 onrthe other handzre'ceives equal.v magnitudes of 0 fl and f2, with f2 reversed from its original phase. which. arethen .used to `modulate thecarrier sideband generator i I2;

some signals from tliefrequency-multiplier I0 and finally to produce "only sidebands ofthe carrier frequency modulated vwith fil l andA f2. 'Ilhissideband energy-from the sideband generator Y l2V .is delivered to the upper antenna? 3 and the modifier antennas- 5;- 6l of the glide path arrange-l The output of the carrier-am-pliierH4 providesfbothY carrier and sidebandsthereof n iocl-` ment.

ness. slight shiftA iri'fphase between theY side--Y Vband generator f2 and the carrier ampliierfgll- -`*retraits#01113?,in?aslght-decrease otsharpnejss titled Instrument Landing Guide-System. The f j r .1, Y

without changing the "patha-ngle. 1

Both the carrier' amplifier` and the 'sid'eb'a'ndgenerator. are excited'- bythe common crystal controlled source Y'1.- .The Y 5 function of thesidebandgenerator i's to receive.`

The energization of the antenna arrangement as described produces equal amounts of modulation frequency sideband energy in all of the an.- tenna arrays while in addition providing carrier frequency energy for the lower array. However, the amount of energy fed to the modifier array relative to the other arrays may be varied in order to provide the desirable path characteristic in the vicinity of touchdown. Upon subsequent reception in a mobile craft, the modulation components may be recovered in a receiver and used to operate a course indicator.

While I have described above the principles of my invention in connection with specific apparatus, and particular modifications thereof, it

is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention.

I claim:

l. An equisignal glide path beacon for guiding a craft vertically to a point on a landing runway comprising upper and lower radiator means spaced to one side of the runway to produce intersecting radiation patterns of distinctive signal characteristics along a course over said runway, an auxiliary directive radiator means mounted adjacent the lower said first radiator means andv directive toward said runway to modify the effective distribution of said patterns, and means for modulating energy radiated from said auxiliary radiator with said distinctive signais.

2. An arrangement as set forth in claim 1, wherein said auxiliary radiator means produces a figure of eight radiation pattern with its null oriented in the direction of a line parallel to said course and passing through said modifier radiator.

3. A radio beacon for providing a glide path system over said course comprising a modifier radiator mounted adjacent said lower array and having a directive radiation pattern directive towards said runway, and means for energizing said modifier array.

4. An arrangement as set forth in claim 3, wherein said modifier radiator comprises two horizontally polarized arrays spaced one half wavelength apart at the frequency of said energy, and so mounted as to have their effective center of radiation directly under said upper radiator.

5. A radio beacon for guiding a craft along a given course comprising an antenna system mounted on one side of said course. said antenna system comprising an upper radiator means and a lower radiator means, a source o1' carrier frequency energy, a source of modulation frequency energy, means for modulating said carrier energy with said modulation frequency energy, means for applying modulated carrier energy of given phase to each of said radiators, means for modifying the radiation pattern of said upper and lower radiators comprising a directive modier radiator means mounted adjacent said lower radiator, and means for energizing said modifier radiator with said modulated carrier frequency energy whereby there is produced a radiant energy pattern effectively defining said course.

6. An arrangement as set forth in claim 5, wherein said modifier radiator means comprise two horizontally polarized radiators spaced one half wave-length apart at said carrier frequency, and so mounted as to have their effective center of radiation directly under said upper radiator.

7. An arrangement as set forth in claim (iJ wherein said upper and lower radiator means are spaced apart a plurality of wavelengths at said carrier frequency. g

8. An arrangement as set forth in claim 7, wherein said lower radiator means is mounted at substantially half the height of said upper radiator above a radiant energy reflecting plane.

9. An arrangement as set forth in claim 3, wherein said source of modulation energy comprises two separate modulation waves, said carrier frequency energy source comprising separate outputs for said upper and modifier radiator means and for said lower radiator means and means for modulating separate ones of said carrier frequency outputs with said modulating waves of given phase.

10. An arrangement as set forth in claim 9, wherein said means for modulating said carrier frequency output comprises means for modulating one of said carrier frequency outputs with both of said modulation waves of a given phase, and means for modulating the other carrier frequency output with one of said modulation waves and with the other modulation wave reversed from its given phase.

11. An arrangement as set forth in claim 10, wherein one of said carrier frequency outputs comprises a carrier sideband generator.

12. An arrangement as set forth in claim 11, comprising means for applying said other carrier frequency output to said lower antenna array and means for applying said sideband generator output to said upper array and to said modifier array.

13. An arrangement as set forth in claim 12, further comprises means for providing a phase displacement between said other carrier frequency output and said sideband generator output before application to said lower and upper antennas respectively.

14. An arrangement as set forth in claim 5, wherein each of said radiator means comprises horizontally polarized elements.

15. An arrangement as set forth in claim 14, wherein said given phase comprises a phase displacement.

CHESTER B. WATTS, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,294,882 Alford Sept. 8, 1942 2,373,090 Alford Apr. 10, 1945 2,379,442 Kandoian July 3, 19.45 2,397,531 Busignies et al. Apr. 2, 1946 2,400,736 Brown May 21, 1946 2,406,734 Alford Sept. 3, 1946 2,406,876 Watts Sept. 3, 1946 2,416,342 Newhouse Feb. 25, 1947 2,419,551 Himmel Apr. 29, 1947 2,433,351 Earp Dec. 30, 1947 2,449,999 Armstrong Sept. 28, 1948 

